1. Field of the Invention
The first aspect of our invention relates generally to industrial cleaning apparatuses, and more specifically to apparatuses for regulating the detergent concentration of an aqueous cleaning solution by recirculating used cleaning solution through a chamber containing solid detergent.
The second aspect of our invention relates generally to spray-type dispensers used to create and dispense a chemical solution from a solid block of the chemical, and more specifically to spray-type dispensers which form a chemical solution of substantially constant concentration from a solid block of chemical by adding fresh water to the solution and dissolving the chemical block with solution as necessary.
2. Description of Related Technology
Many industrial cleaning applications require that large objects, such as engine blocks, be soaked in or sprayed with an aqueous detergent solution. The nature of the object being cleaned in conjunction with the design limitations of the cleaning apparatus often prevent significant agitation of either the object or the solution during cleaning. Effective cleaning can therefore only be accomplished by the use of a powerful cleaning agent such as potassium hydroxide. Due to the adherent nature of the accumulated deposits typically encountered in such situations, the residence times of the objects in the cleaning vat or chamber may be several hours. Since the cleaning chambers often have capacities of 1000 gallons or more, frequent changes of the aqueous detergent solution is impractical. The same solution may remain within the tank for months.
The caustic cleaning agents typically employed in industrial cleaning are produced commercially in particulate form such as flakes, powder, beads, crystals, etc and are introduced directly into the water in the cleaning vat or chamber by means of a shovel or small container. The particles present a relatively large surface area as compared to their total volume and, when suddenly introduced into the water in the vat, often produce a violent exothermic reaction. The production of steam can occur so rapidly that hot, caustic liquid may splatter, endangering the person placing the particles in the vat.
Alternately, the detergent may be hand-fed into an intermediate dissolving chamber and then subsequently contacted with water in order to dissolve the detergent before its introduction into the cleaning tank.
The instantaneous concentration of the aqueous detergent solution can vary considerably when the cleaning agent is introduced into the intermediate chamber in this manner, since the most soluble ingredients and those with the smallest particle size will dissolve first. Such variations in concentration of the various detergent components are wasteful of detergent and result in a poorly controlled cleaning operation.
In order to avoid the hazards associated with dry particulate detergent, some manufacturers dissolve the detergent in water and supply the resulting liquid detergent to the customer. Although this method is safer, the resulting solution is typically at least 70% water in order to maintain solubility of the detergent components during typical shipping and storage conditions. The customer is therefore required to pay a premium for water as the water must be blended, packaged, stored and shipped.
An ideal cleaning system would include a means for (i) constantly measuring the detergent concentration in the cleaning solution, (ii) maintaining a constant detergent concentration, (iii) safely introducing additional detergent into the cleaning solution when required to maintain a constant detergent concentration (hopefully by a relatively passive, if not automatic, means not requiring handling of the material by an operator), and (iv) recycling the aqueous detergent solution so that water, cleaning agent and energy are conserved to the maximum extent possible. Further, the system must lend itself to cleaning operations which take up to several hours per object, while requiring complete replacement of the cleaning solution only once a month or so.
The best choice for a detergent would be a solid having the lowest possible ratios of surface area/volume and surface area/weight.
One approach used by cleaning system designers to achieve the goal of obtaining a constant aqueous detergent solution concentration is to continuously supply detergent to the solution at a constant rate. For example, U.S. Pat. No. 2,371,720, issued to Stine, discloses a method whereby a granular cleaning agent (C) is placed within a chamber on a screen (8) so as to present a uniform surface area to a continuous spray of water (W). The eroding effect of the water as it contacts the cleaning agent causes a highly concentrated aqueous detergent solution to flow by gravity into a cleaning tank. The system is designed so that even though the detergent supply gradually diminishes the surface area of the detergent in contact with the water remains relatively constant. The amount of water supplied by the spray nozzle is controlled solely by conventional, manually controlled valves or alternatively, a proportioning valve which supplies an amount of water to the spray nozzle which is proportional to the amount of water which is simultaneously being supplied to the cleaning vat or chamber. Although this system is mechanically simple, its ability to continuously supply detergent at a constant rate is inhibited by the tendency of the detergent particles to pack or harden during idle periods when the water supply is intentionally interrupted.
A closed loop system employing a constant rate detergent dispensing device is disclosed in U.S. Pat. No. 3,066,520, issued to Jennings. In the Jennings system, a predetermined amount of a granular detergent (40) is placed in a chamber (39), wherein the detergent is continuously subjected to a stream of water which is diverted from a main washing basin (4). The amount of granular detergent placed within the chamber is based upon an idealized assumption of the rate of detergent consumption in the washing basin. No method of measuring the actual detergent concentration in the washing basin is provided, which, while suitable for cleaning operations of relatively short duration, is unsuitable for operations which extend for a period of hours or days during which time the rate of detergent consumption may be highly variable.
A more sophisticated closed loop cleaning system is disclosed in U.S. Pat. No. 3,355,324, issued to Catzen. The Catzen device continuously recirculates aqueous detergent solution past a concentrated detergent solution source (30), but limits the amount of concentrated detergent solution that is added to the aqueous detergent solution by means of a valve (38). The valve is operated manually based upon a predetermined sequence of events. No method is provided for actually measuring detergent concentration in the aqueous detergent solution.
An apparatus that does monitor various parameters in a closed loop cleaning system is disclosed in U.S. Pat. No. 4,076,554, issued to Weihe. However, the Weihe device measures only fluid flow rates in an attempt to monitor the cost of operating the cleaning system.
U.S. Pat. No. 3,595,252, issued to Conte, discloses a closed loop monitoring system used in conjunction with a glassware cleaning apparatus. The Conte device utilizes conductivity measuring means to ascertain the specific resistance of the water used to clean the glassware and thereby determine the degree of purity of the water. The Conte device cleans only with deionized water and therefore does not address the problems associated with the introduction of detergent into the cleaning media.
A recirculating cleaning system is disclosed in U.S. Pat. No. 3,085,416, issued to D'Hooge. The D'Hooge device constantly recirculates aqueous detergent solution past a hygrometer which measures the relative humidity of the air immediately above the solution. When the humidity drops below a certain level, a valve automatically opens and introduces additional water into the cleaning basin from a separate tank. If the relative humidity rises above a certain level, additional detergent is supplied from a separate container to the main cleaning basin by means of a remotely operated valve. Thus, in the D'Hooge system the aqueous detergent solution is recirculated only to facilitate sampling and does not play a direct role in increasing or decreasing the concentration of the solution.
Another concentration monitoring and adjustment system is disclosed in U.S. Pat. No. 4,463,582, issued to Saalmann. The Saalmann device continuously measures detergent concentration in the main washing basin. When the concentration drops below some preset value, additional dry cleaning agent is mixed with water at a separate location and then introduced into the main washing basin. This system has the advantage of permitting a caustic substance to be mixed in relative isolation and introduced into the tank without interaction by a human operator.
Each of the devices herein described, while satisfactory for their intended purpose, leaves something to be desired that they are complex in design, costly, require the proper execution of a variety of sequential steps and/or are inefficient in the utilization of water, cleaning agent and/or energy.
Dispenser
Several industrial applications require the formation and dispensing of an aqueous chemical solution from a solid, as opposed to particulate, form of the chemical. One such device is the spray-type dispenser which forms a concentrated chemical solution from a solid block of the chemical by spraying the solid block of chemical with water so as to dissolve a portion of the chemical block. The chemical solution thus formed is then allowed to immediately pass out of the device and can be either directed to its utilization point or stored in a reservoir.
While overcoming the problem of varying solubility rates of various components in the solid chemical, one difficulty encountered with spray-type dispensers is their inability to form a chemical solution of substantially constant concentration over the entire lifetime of a single block of chemical.
A first approach at overcoming the difficulty is presented in U.S. Pat. No. 3,595,438, issued to Daley, which discloses a spray-type dispenser for converting particulate detergent into a concentrated detergent solution by spraying a mass of the detergent with water in response to a signal that the volume of detergent solution retained within a reservoir has decreased below a preset amount.
A second approach at overcoming the difficulty is presented in U.S. Pat. No. 4,020,865, issued to Moffatt et al, which discloses a spray-type dispenser for converting particulate detergent into a concentrated detergent solution by spraying a mass of the detergent with detergent solution from a reservoir of the solution whenever solution is dispensed from the reservoir. Make-up water is added directly to the reservoir.
A third approach at overcoming the difficulty is presented in U.S. Pat. No. 4,063,663, issued to Larson, which discloses a spray-type dispenser for converting particulate detergent into a concentrated detergent solution by spraying a mass of the detergent with fresh water in response to a signal from a pair of electrodes in the use solution that concentration of detergent in the use solution is below a predetermined minimum.
While each of the Daley, Moffatt, and Larson devices represents an advance over prior attempts, the search continues for a system capable of effectively creating a substantially constant volume of a concentrated chemical solution from a solid block of chemical wherein the solution has a substantially constant concentration over time regardless of a change in dispensing parameters.